How strong is the link between antibiotic use and resistance? Patients with upper respiratory tract infections (URTIs) have come to expect an antibiotic even if their clinical presentation is consistent with a viral infection.
How strong is the link between antibiotic use and resistance?
Patients with upper respiratory tract infections (URTIs) have come to expect an antibiotic even if their clinical presentation is consistent with a viral infection. In a Consultant editorial last year, I discussed the “scourge” of Clostridium difficile colitis that has resulted from the expanding use of traditional as well as newly discovered antibiotics.1 The issue has become prominent because an increasing number of persons have severe C difficile colitis that requires surgery.
RAPID RISE IN RESISTANT STRAINS
A recent study suggests that there is another reason to curtail the use of outpatient antibiotics: the rapid development of resistance. Investigators in Belgium demonstrated that 2 commonly prescribed antibiotics, azithromycin and clarithromycin, can induce resistance within days.2,3 In this study, 224 persons were randomly assigned to azithromycin, clarithromycin, or placebo (because the 2 antibiotics are delivered differently, there were 2 placebo groups). The outcome chosen for study was the effect of each antibiotic on the normal flora in the throat at day 4 (azithromycin) and day 8 (clarithromycin) respectively, as well as at other intervals.
The results are disturbing. Both antibiotics increased the proportion of macrolide-resistant bacteria. At day 4 of azithromycin therapy, there was a 53.4% increase in resistant bacteria when compared with placebo (P < .0001). For clarithromycin, the increase was 50% (P < .0001). Azithromycin resulted in a higher proportion of resistance than clarithromycin. The largest difference between the 2 antibiotics was 17.4% at day 28 (greater resistance with azithromycin). Just in case one is motivated to favor clarithromycin based on these data, the resistance gene selected for with clarithromycin therapy confers a higher level of resistance than the gene associated with azithromycin.
How long do these serious alterations in normal flora last? A single course of either antibiotic continued to resonate, with increased resistance, 180 days after the treatment ended.
NEED FOR ANTIBIOTIC STEWARDSHIP
Many problematic organisms today, such as methicillin-resistant Staphylococcus aureus and a host of Gram-negatives, prove “neo-Darwinism” is at work whenever we invent antibiotics to kill bacteria.4 Antibiotic stewardship is a reality, even if some view it as a threat to practitioner autonomy. We have to be “resistant” to patients’ expectation of antibiotics for URTIs as well as many other maladies.
What hath antibiotics wrought? The nightmare of Clostridium difficile colitis.
Malhotra-Kumar S, Lammens C, Coenen S, et al. Effect of azithromycin and clarithromycin therapy on pharyngeal carriage of macrolide-resistant streptococci in healthy volunteers: a randomised, double-blind, placebo-controlled study.
Dancer SJ. Attention prescribers: be careful with antibiotics.
Methicillin-resistant staph on the rise-and on the loose.